Metal oxide ceramic materials have been investigated for their use in ICs. For example, metal oxide ceramics that are ferroelectrics or are capable of being transformed into ferroelectrics are useful due to their high remanent polarization (2Pr) and reliable long-term storage characteristics. Non-ferroelectric metal oxide ceramics, such as superconductors, have also been investigated.
Various techniques, such as sol-gel, chemical vapor deposition (CVD), sputtering, or pulsed laser deposition (PLD), have been developed for depositing ferroelectric films on a substrate. Such techniques, for example, are described, for example, Budd et al., Brit. Ceram. Soc. Proc., 36, p107 (1985); Brierley et al., Ferroelectrics, 91, p181 (1989), Takayama et al., J. Appl. Phys., 65, p1666 (1989); Morimoto et al., J. Jap. Appl. Phys. 318, 9296 (1992); and co-pending U.S. patent applications Ser. No. 08/975,087, titled "Low Temperature CVD Process using B-Diketonate Bismuth Precursor for the Preparation of Bismuth Ceramic Thin Films for Integration into Ferroelectric Memory Devices," U.S. Ser. No. 09/107,861, titled "Amorphously Deposited Metal Oxide Ceramic Films," all of which are herein incorporated by reference for all purposes.
Metal oxide ceramics are often treated with a post-deposition thermal process at a relatively high temperature in order to produce resulting materials with the desired electrical characteristics. For example, some Bi-based oxide ceramics such as strontium bismuth tantalate (SBT) are thermally treated by a "ferroanneal." The ferroanneal converts the as-deposited films into the ferroelectric phase. After the as-deposited films are converted into the ferroelectric phase, the ferroanneal continues, growing the grain size (e.g., greater than about 180 nm) of the films in order to achieve a good remanent polarization. Other types of metal oxide ceramics can be deposited as ferroelectrics. For example, lead zirconium titanate (PZT) is often deposited at relatively higher temperatures, such as greater than 500.degree. C., to form an as-deposited film with a ferroelectric perovskite phase. Although the PZT is generally deposited as a ferroelectric, a post-deposition thermal process is often still needed to improve its electrical characteristics.
Typically, the metal oxide ceramic materials contain a mobile specie which easily diffuses into other regions of the IC. Diffusion of the mobile specie into other regions can have a detrimental effect on the performance and functionality of the IC. For example, in the case of Bi-based oxide ceramics, the diffusion of Bi into other regions of the IC can alter stress, cause shorts and/or alter the electrical properties of the diffusion regions of devices, thus adversely impacting functionality of the IC.
In view of the foregoing discussion, it is desirable to prevent unwanted diffusion of a mobile specie from a metal oxide ceramic material.